Question

Probability that 10-digit number is divisible by 4 both with, and without repetition.

Answer 1

There are 9×103=9000 total possibilities for all 4 digits.

The number can be divided by 4 if the last 2 digits are a multiple of 4. So - 00,04,08,...,96 (25 possibilities).

So, there are 25 possibilities for the last 2 digits, 9 for the first digit, and 10 for the second digit.

Therefore, P(divisible by 4 w/replacement) = 9×10×259000